This invention relates to an electronic device, such as a large-scale integrated circuit, comprising a considerably complicated logic circuit and/or the like.
Logic circuits are functionally classified into a combinational and a sequential circuit in the art. A combinational circuit comprises an AND gate, an OR gate, and/or a similar circuit. A sequential circuit comprises a register, a flip-flop circuit or a memory cell, and/or a like circuit. Test of a combinational circuit is comparatively easy. Test of a sequential circuit is somewhat difficult. For the test of a sequential circuit, a proposal has been made according to which all circuit components, such as registers, are cascade-connected into a shift register. A test data signal of a predetermined time-sequential pattern is supplied to the re-connected circuit components to derive an output signal for the test. This proposal is not effective when the logic circuit comprises a great number of memory cells or the like because it is too troublesome and adversely affects the test efficiency to re-connect the registers and the like into a single shift register. Moreover, the test is very difficult when an electronic device including a logic circuit comprises at least one oscillator. This is because it is difficult to freely control the oscillator from a peripheral circuit, such as a testing installation. In order to facilitate description of the instant invention, a considerable number of memory cells and/or like circuits and/or at least one oscillator will be called an electronic circuit throughout the specification.